Economic benefit of ecological remediation of mercury pollution in southwest China 2007-2022.

Methylmercury (MeHg) exposure via rice consumption poses health risk to residents in mercury contaminated areas, such as the Wanshan Hg mining area (WSMA) in southwest China. Making use of the published data for WSMA, this study developed a database of rice MeHg concentrations for different villages in this region for the years of 2007, 2012, 2017, and 2019. The temporal changes of human MeHg exposure, health effects, and economic benefits under different ecological remediation measures were then assessed. Results from this study revealed a decrease of 3.88 µg/kg in rice MeHg concentration and a corresponding reduction of 0.039 µg/kg/d in probable daily intake of MeHg in 2019 compared to 2007 on regional average in the WSMA. Ecological remediation measures in this region resulted in the accumulated economic benefits of $38.7 million during 2007-2022, of which 84 % was from pollution source treatment and 16 % from planting structure adjustment. However, a flooding event in 2016 led to an economic loss of $2.43 million (0.38 % of regional total Gross Domestic Product). Planting structure adjustment generates the greatest economic benefits in the short term, whereas pollution source treatment maximizes economic benefits in the long term and prevents the perturbations from flooding event. These findings demonstrate the importance of ecological remediation measures in Hg polluted areas and provide the foundation for risk assessment of human MeHg exposure via rice consumption.

Calcite carbonate sinks low-density plastic debris in open oceans.

The vertical settling of plastic debris in oceans is poorly understood. A large share of low-density microplastics (LDMPs) are largely absent from sea surfaces. The present study employs a model that considers the potential of an overlooked microbially induced calcium carbonate precipitation (MICP) process and new motion equations for irregular LDMPs. Here we show that the motion of LDMPs in the present model, exhibiting a damped oscillation pattern, is quite different from that in biofouling models. Furthermore, LDMPs in the size range of 10-200 µm are most likely to gain sufficient density at the biofouling/MICP stage to independently sink to the ocean floor with relatively small drag coefficients, potentially explaining the selective enrichment of LDMPs in the oceanic sediment. The size and shape exhibit strong non-linear effects on the settling patterns of LDMPs. Overall, the present study highlights the importance of calcite-mediated sinking of LDMPs in open oceans.

Potential decoupling of CO2 and Hg uptake process by global vegetation in the 21st century.

Mercury (Hg), a potent neurotoxin posing risks to human health, is cycled through vegetation uptake, which is susceptible to climate change impacts. However, the extent and pattern of these impacts are largely unknown, obstructing predictions of Hg's fate in terrestrial ecosystems. Here, we evaluate the effects of climate change on vegetation elemental Hg [Hg(0)] uptake using a state-of-the-art global terrestrial Hg model (CLM5-Hg) that incorporates plant physiology. In a business-as-usual scenario, the terrestrial Hg(0) sink is predicted to decrease by 1870 Mg yr-1 in 2100, that is ~60% lower than the present-day condition. We find a potential decoupling between the trends of CO2 assimilation and Hg(0) uptake process by vegetation in the 21st century, caused by the decreased stomatal conductance with increasing CO2. This implies a substantial influx of Hg into aquatic ecosystems, posing an elevated threat that warrants consideration during the evaluation of the effectiveness of the Minamata Convention.

Isotope Data Constrains Redox Chemistry of Atmospheric Mercury.

The redox chemistry of mercury (Hg) in the atmosphere exerts a significant influence on its global cycle. However, our understanding of this important process remains shrouded in uncertainty. In this study, we utilize three-dimensional atmospheric Hg isotope modeling to evaluate the isotopic composition of particle-bound mercury [HgII(P)] in the global atmosphere. We investigate various chemistry mechanisms and find that they induce remarkably disparate odd-number mass-independent fractionation (odd-MIF) in HgII(P) on a global scale. The observed odd-MIF data identify the essential role of sea salt aerosol debromination in the redox chemistry of atmospheric Hg and underscore the predominant influence of Br oxidation in the marine boundary layer. The odd-MIF signatures significantly narrow the uncertainty range of redox chemistry rates and constrain the photoreduction of HgII(P) at a magnitude of 10-3 JNO2 (local photolysis frequency of NO2) in the global atmosphere. This study advances our understanding of atmospheric Hg chemistry processes and provides insights into the potential impacts of climate change on Hg cycling.

Study on the Nanoaggregate Formation Mechanism and Antipyretic Effect of Maxing Shigan Decoction.

Traditional Chinese medicine (TCM) formula decoctions easily form nanoaggregates due to self-assembly during the decoction process. However, research on nanoaggregates in TCM is still in its infancy with limited systematic studies. Maxing Shigan Decoction (MXSGT), a TCM formula, has been commonly used for the treatment of fever for thousands of years in China. This study used MXSGT as an example to investigate the antipyretic effects of MXSGT nanoaggregates (MXSGT-NAs) in its decoction, shedding light on the compatibility mechanisms of Chinese medicine. MXSGT-NAs were isolated by using high-speed centrifugation and dialysis techniques. The morphology, particle size distribution, and electrical potential of MXSGT-NAs were characterized. High-performance liquid chromatography (HPLC) was used to detect ephedrine and pseudoephedrine in MXSGT-NAs. The self-assembly mechanism of MXSGT-NAs was investigated by deconstructing the prescription. In pharmacodynamic experiments, a rat fever model was established through the subcutaneous injection of dry yeast to investigate the antipyretic effects of MXSGT-NAs. The results showed the presence of regularly shaped spherical nanoaggregates in MXSGT. It contains carbon, oxygen (O), sulfur (S), sodium, aluminum (Al), calcium (Ca), iron, magnesium, bismuth (Bi), etc. MXSGT-NAs exerted substantial antipyretic effects on febrile rats. Furthermore, we found micrometer-sized particles composed of Ca, O, S, potassium, and Bi in Shi gao decoctions. This study is the first to provide evidence for the self-assembling property of Shi gao, elucidate the scientific connotation of dispensing Shi gao in MXSGT, and provide a novel perspective for the study of TCM decoctions.

A hidden demethylation pathway removes mercury from rice plants and mitigates mercury flux to food chains.

Dietary exposure to methylmercury (MeHg) causes irreversible damage to human cognition and is mitigated by photolysis and microbial demethylation of MeHg. Rice (Oryza sativa L.) has been identified as a major dietary source of MeHg. However, it remains unknown what drives the process within plants for MeHg to make its way from soils to rice and the subsequent human dietary exposure to Hg. Here we report a hidden pathway of MeHg demethylation independent of light and microorganisms in rice plants. This natural pathway is driven by reactive oxygen species generated in vivo, rapidly transforming MeHg to inorganic Hg and then eliminating Hg from plants as gaseous Hg°. MeHg concentrations in rice grains would increase by 2.4- to 4.7-fold without this pathway, which equates to intelligence quotient losses of 0.01-0.51 points per newborn in major rice-consuming countries, corresponding to annual economic losses of US$30.7-84.2 billion globally. This discovered pathway effectively removes Hg from human food webs, playing an important role in exposure mitigation and global Hg cycling.

Predicting high-resolution air quality using machine learning: Integration of large eddy simulation and urban morphology data.

Accurately predicting air pollutants, especially in urban areas with well-defined spatial structures, is crucial. Over the past decade, machine learning techniques have been widely used to forecast urban air quality. However, traditional machine learning approaches have limitations in accuracy and interpretability for predicting pollutants. In this study, we propose a convolutional neural network (CNN) model to predict the spatial distribution of CO concentration in Nanjing urban area at 10 m resolution. Our model incorporates various factors as input, such as building height, topography, emissions, and is trained against the outputs simulated by the parallelized large-eddy simulation model (PALM). The PALM model has 48 different scenarios that varied in emissions, wind speeds, and wind directions. The results display a strong consistency between the two models. Furthermore, we evaluate the performance of our model using a 10-fold cross-validation and out-of-sample cross-validation approach. This yields a robust correlation (with both R2 > 0.8) and a low RMSE between the CO predicted by the PALM and CNN models, which demonstrates the generalization capability of our CNN model. The CNN can extract crucial features from the resulted weight contribution map. This map indicates that the CO concentration at a location is more influenced by nearby buildings and emissions than distant ones. The interpretable patterns uncovered by our model are related to neighborhood effects, wind speeds, directions, and the impact of orientation on urban CO distribution. The model also shows high prediction accuracy (R > 0.8) when applied to another city. Overall, the integration of our CNN framework with the PALM model enhances the accuracy of air quality predictions, while enabling a fluid dynamic laws interpretation, providing effective tools for air quality management.

Rationale and design of the GOLDEN BRIDGE II: a cluster-randomised multifaceted intervention trial of an artificial intelligence-based cerebrovascular disease clinical decision support system to improve stroke outcomes and care quality in China.

BACKGROUND: Given the swift advancements in artificial intelligence (AI), the utilisation of AI-based clinical decision support systems (AI-CDSSs) has become increasingly prevalent in the medical domain, particularly in the management of cerebrovascular disease. AIMS: To describe the design, rationale and methods of a cluster-randomised multifaceted intervention trial aimed at investigating the effect of cerebrovascular disease AI-CDSS on the clinical outcomes of patients who had a stroke and on stroke care quality. DESIGN: The GOLDEN BRIDGE II trial is a multicentre, open-label, cluster-randomised multifaceted intervention study. A total of 80 hospitals in China were randomly assigned to the AI-CDSS intervention group or the control group. For eligible participants with acute ischaemic stroke in the AI-CDSS intervention group, cerebrovascular disease AI-CDSS will provide AI-assisted imaging analysis, auxiliary stroke aetiology and pathogenesis analysis, and guideline-based treatment recommendations. In the control group, patients will receive the usual care. The primary outcome is the occurrence of new vascular events (composite of ischaemic stroke, haemorrhagic stroke, myocardial infarction or vascular death) at 3 months after stroke onset. The sample size was estimated to be 21 689 with a 26% relative reduction in the incidence of new composite vascular events at 3 months by using multiple quality-improving interventions provided by AI-CDSS. All analyses will be performed according to the intention-to-treat principle and accounted for clustering using generalised estimating equations. CONCLUSIONS: Once the effectiveness is verified, the cerebrovascular disease AI-CDSS could improve stroke care and outcomes in China. TRIAL REGISTRATION NUMBER: NCT04524624.

Large-scale renewable energy brings regionally disproportional air quality and health co-benefits in China.

Developing renewable energy could jointly reduce air pollution, greenhouse gas emissions, and bring air pollution-related health co-benefits. However, the temporal and sub-national distributions of investment costs and human health co-benefits from renewable energy deployment remain unclear. To investigate this gap, we linked multiple models for a more comprehensive assessment of the economic-environmental-health co-benefits of renewable energy development in China. The results show that developing renewable energy can avoid 0.6 million premature mortalities, 151 million morbidities, and 111 million work-loss days in 2050. Meanwhile, the human health and economic co-benefits vary substantially across regions in China. Renewable energy can undoubtedly bring health and economic co-benefits. Nevertheless, the economic benefits lag considerably behind the high initial investment cost, first negative in 2030 (-0.6 trillion Yuan) and then positive in 2050 (2.9 trillion Yuan). Hence, renewable energy deployment strategy must be carefully designed considering the regional disparities.

Modeling the Mercury Cycle in the Sea Ice Environment: A Buffer between the Polar Atmosphere and Ocean.

Sea ice (including overlying snow) is a dynamic interface between the atmosphere and the ocean, influencing the mercury (Hg) cycling in polar oceans. However, a large-scale and process-based model for the Hg cycle in the sea ice environment is lacking, hampering our understanding of regional Hg budget and critical processes. Here, we develop a comprehensive model for the Hg cycle at the ocean-sea ice-atmosphere interface with constraints from observational polar cryospheric data. We find that seasonal patterns of average total Hg (THg) in snow are governed by snow thermodynamics and deposition, peaking in springtime (Arctic: 5.9 ng/L; Antarctic: 5.3 ng/L) and minimizing during ice formation (Arctic: 1.0 ng/L, Antarctic: 0.5 ng/L). Arctic and Antarctic sea ice exhibited THg concentration peaks in summer (0.25 ng/L) and spring (0.28 ng/L), respectively, governed by different snow Hg transmission pathways. Antarctic snow-ice formation facilitates Hg transfer to sea ice during spring, while in the Arctic, snow Hg is primarily moved through snowmelt. Overall, first-year sea ice acts as a buffer, receiving atmospheric Hg during ice growth and releasing it to the ocean in summer, influencing polar atmospheric and seawater Hg concentrations. Our model can assess climate change effects on polar Hg cycles and evaluate the Minamata Convention's effectiveness for Arctic populations.

Mercury budgets in the suspended particulate matters of the Yangtze River.

Riverine processes are crucial for the biogeochemical cycle of mercury (Hg). The Yangtze River, the largest river in East Asia, discharges a substantial amount of Hg into the East China Sea. However, the influencing factors of the Hg budget and its recent trends remain unclear. This study quantitatively analyzed the total Hg concentration (THg) in suspended particulate matter (SPM) in the Yangtze River and calculated the Hg budget in 2018 and 2021. The results showed that the total Hg concentrations varied substantially along the river, with concentrations ranging from 23 to 883 µg/kg in 2018 and 47 to 146 µg/kg in 2021. The average Hg flux to China Sea in 2018 and 2021 were approximately 10 Mg/yr, lower than in 2016 (48 Mg/yr). Over 70% of the SPM was trapped in the Three Gorges Dam (TGD), and 22 Mg/yr of Hg settled in the TGD in 2018 and 10 Mg/yr in 2021. Hg fluxes in the Yangtze River watershed were driven by various factors, including decreased industrial emissions, increased agriculture emissions, and decreased soil erosion flux. We found that in the upper reach of the Yangtze River changed from sink to source of Hg possibly due to the resuspension of sediments, which implies that the settled sediments could be a potential source of Hg for downstream. Overall, emission control policies may have had a positive impact on reducing Hg flux to the East China Sea from 2016 to 2021, but more efforts are needed to further reduce Hg emissions.

Enhanced daytime atmospheric mercury in the marine boundary layer in the South Oceans.

Understanding the spatial and temporal variations of atmospheric mercury (Hg) in the marine boundary layer could advance our knowledge on ocean evasion of Hg. Here, we conducted continuous measurements of total gaseous mercury (TGM) in the marine boundary layer during a round-the-world cruise from August 2017 to May 2018. We observed the highest and lowest TGM concentrations in Southern Indian Ocean (1.29 ± 0.22 ng m-3) and Southern Atlantic Ocean (0.61 ± 0.28 ng m-3), respectively. During the daytime, enhanced TGM was observed with the diurnal amplitude difference reaching its maximum in the range of 0.30-0.37 ng m-3 in Southern Indian Ocean and Southern Ocean. The positive correlation between TGM (R2 = 0.68-0.92) and hourly solar radiation in each ocean suggested that the daytime enhanced TGM was likely driven by Hg photoreduction in seawater, after excluding the influence of other meteorological factors. The diurnal amplitude of TGM in the marine boundary layer might be impacted by the microbial productivity and the ratio of ultraviolet radiation. Our study highlights that ocean acts as a net TGM source during the daytime in the Southern Hemisphere and aqueous photoreduction process may play an important role in the biogeochemical cycling of Hg.

International trade shapes global mercury-related health impacts.

Mercury (Hg) is a strong neurotoxin with substantial dangers to human health. Hg undergoes active global cycles, and the emission sources there of can also be geographically relocated through economic trade. Through investigation of a longer chain of the global biogeochemical Hg cycle from economic production to human health, international cooperation on Hg control strategies in Minamata Convention can be facilitated. In the present study, four global models are combined to investigate the effect of international trade on the relocation of Hg emissions, pollution, exposure, and related human health impacts across the world. The results show that 47% of global Hg emissions are related to commodities consumed outside of the countries where the emissions are produced, which has largely influenced the environmental Hg levels and human exposure thereto across the world. Consequently, international trade is found to enable the whole world to avoid 5.7 × 105 points for intelligence quotient (IQ) decline and 1,197 deaths from fatal heart attacks, saving a total of $12.5 billion (2020 USD) in economic loss. Regionally, international trade exacerbates Hg challenges in less developed countries, while resulting in an alleviation in developed countries. The change in economic loss therefore varies from the United States (-$4.0 billion) and Japan (-$2.4 billion) to China (+$2.7 billion). The present results reveal that international trade is a critical factor but might be largely overlooked in global Hg pollution mitigation.

Toward a Global Model of Methylmercury Biomagnification in Marine Food Webs: Trophic Dynamics and Implications for Human Exposure.

Marine fish is an excellent source of nutrition but also contributes the most to human exposure to methylmercury (MMHg), a neurotoxicant that poses significant risks to human health on a global scale and is regulated by the Minamata Convention. To better predict human exposure to MMHg, it is important to understand the trophic transfer of MMHg in the global marine food webs, which remains largely unknown, especially in the upper trophic level (TL) biota that is more directly relevant to human exposure. In this study, we couple a fish ecological model and an ocean methylmercury model to explore the influencing factors and mechanisms of MMHg transfer in marine fish food webs. Our results show that available MMHg in the zooplankton strongly determines the MMHg in fish. Medium-sized fish are critical intermediaries that transfer more than 70% of the MMHg circulating in food webs. Grazing is the main factor to control MMHg concentrations in different size categories of fish. Feeding interactions affected by ecosystem structures determine the degree of MMHg biomagnification. We estimate a total of 6.1 metric tons of MMHg potentially digested by the global population per year through marine fish consumption. The model provides a useful tool to quantify human exposure to MMHg through marine fish consumption and thus fills a critical gap in the effectiveness evaluation of the convention.

Buffering effect of global vegetation on the air-land exchange of mercury: Insights from a novel terrestrial mercury model based on CESM2-CLM5.

The vegetation uptake of atmospheric elemental mercury [Hg(0)] and its subsequent littering are critical processes of the terrestrial Hg cycles. There is a large uncertainty in the estimated global fluxes of these processes due to the knowledge gap in the underlying mechanisms and their relationship with environmental factors. Here, we develop a new global model based on the Community Land Model Version 5 (CLM5-Hg) as an independent component of the Community Earth System Model 2 (CESM2). We explore the global pattern of gaseous elemental Hg [Hg(0)] uptake by vegetation and the spatial distribution of litter Hg concentration constrained by observed datasets as well as its driving mechanism. The annual vegetation uptake of Hg(0) is estimated as 3132 Mg yr-1, which is considerably higher than previous global models. The scheme of dynamic plant growth including stomatal activities substantially improves the estimation for global terrestrial distribution of Hg, compared to the leaf area index (LAI) based scheme that is often used by previous models. We find the global distribution of litter Hg concentrations driven by vegetation uptake of atmospheric Hg(0), which are simulated to be higher in East Asia (87 ng/g) than in the Amazon region (63 ng/g). Meanwhile, as a significant source for litter Hg, the formation of structural litter (cellulose litter + lignin litter) results in a lagging effect between Hg(0) deposition and litter Hg concentration, implying the buffering effect of vegetation on the air-land exchange of Hg. This work highlights the importance of vegetation physiology and environmental factors in understanding the vegetation sequestration of atmospheric Hg globally, and calls for greater efforts to protect forests and afforestation.

Elevated methylmercury in Antarctic surface seawater: The role of phytoplankton mass and sea ice.

Methylmercury is a neurotoxin that is biomagnified in marine food webs. Its distribution and biogeochemical cycle in Antarctic seas are still poorly understood due to scarce studies. Here, we report the total methylmercury profiles (up to 4000 m) in unfiltered seawater (MeHgT) from the Ross Sea to the Amundsen Sea. We found high MeHgT levels in oxic unfiltered surface seawater (upper 50 m depth) in these regions. It was characterized by an obviously higher maximum concentration level of MeHgT (up to 0.44 pmol/L, at a depth of 3.35 m), which is higher than other open seas (including the Arctic Ocean, the North Pacific Ocean and the equatorial Pacific), and a high MeHgT average concentration in the summer surface water (SSW, 0.16 ± 0.12 pmol/ L). Further analyses suggest that the high phytoplankton mass and sea-ice fraction are important drivers of the high MeHgT level that we observed in the surface water. For the influence of phytoplankton, the model simulation showed that the uptake of MeHg by phytoplankton would not fully explain the high levels of MeHgT, and we speculated that high phytoplankton mass may emit more particulate organic matter as microenvironments that can sustain Hg in-situ methylation by microorganisms. The presence of sea-ice may not only harbor a microbial source of MeHg to surface water but also trigger increased phytoplankton mass, facilitating elevation of MeHg in surface seawater. This study provides insight into the mechanisms that impact the content and distribution of MeHgT in the Southern Ocean.

Global change effects on biogeochemical mercury cycling.

Past and present anthropogenic mercury (Hg) release to ecosystems causes neurotoxicity and cardiovascular disease in humans with an estimated economic cost of $117 billion USD annually. Humans are primarily exposed to Hg via the consumption of contaminated freshwater and marine fish. The UNEP Minamata Convention on Hg aims to curb Hg release to the environment and is accompanied by global Hg monitoring efforts to track its success. The biogeochemical Hg cycle is a complex cascade of release, dispersal, transformation and bio-uptake processes that link Hg sources to Hg exposure. Global change interacts with the Hg cycle by impacting the physical, biogeochemical and ecological factors that control these processes. In this review we examine how global change such as biome shifts, deforestation, permafrost thaw or ocean stratification will alter Hg cycling and exposure. Based on past declines in Hg release and environmental levels, we expect that future policy impacts should be distinguishable from global change effects at the regional and global scales.

Plastic waste discharge to the global ocean constrained by seawater observations.

Marine plastic pollution poses a potential threat to the ecosystem, but the sources and their magnitudes remain largely unclear. Existing bottom-up emission inventories vary among studies for two to three orders of magnitudes (OMs). Here, we adopt a top-down approach that uses observed dataset of sea surface plastic concentrations and an ensemble of ocean transport models to reduce the uncertainty of global plastic discharge. The optimal estimation of plastic emissions in this study varies about 1.5 OMs: 0.70 (0.13-3.8 as a 95% confidence interval) million metric tons yr-1 at the present day. We find that the variability of surface plastic abundance caused by different emission inventories is higher than that caused by model parameters. We suggest that more accurate emission inventories, more data for the abundance in the seawater and other compartments, and more accurate model parameters are required to further reduce the uncertainty of our estimate.

Effect of Coal Mining on Soil Microorganisms from Stipa krylovii Rhizosphere in Typical Grassland.

The environmental changes caused by coal mining activities caused disturbances to the plant, soil, and microbial health in the mining area. Arbuscular mycorrhizal fungi (AMF) play an important role in the ecological restoration of mining areas. However, it is less understood how soil fungal communities with multiple functional groups respond to coal mining, and the quantitative impact and risk of mining disturbance. Therefore, in this study, the effect of coal mining on soil microorganisms' composition and diversity were analyzed near the edge of an opencast coal-mine dump in the Shengli mining area, Xilingol League, Inner Mongolia. The response strategy of soil fungi to coal mining and the stability of arbuscular mycorrhizal fungi (AMF) in the soil fungal community were determined. Our results showed that coal mining affected AMF and soil fungi in areas within 900 m from the coal mine. The abundance of endophytes increased with the distance between sampling sites and the mine dump, whereas the abundance of saprotroph decreased with the distance between sampling sites and the mine dump. Saprotroph was the dominant functional flora near the mining area. The nodes percentage of Septoglomus and Claroideoglomus and AMF phylogenetic diversity near the mining area were highest. AMF responded to the mining disturbance via the variety and evolution strategy of flora. Furthermore, AMF and soil fungal communities were significantly correlated with edaphic properties and parameters. Soil available phosphorus (AP) was the main influencer of soil AMF and fungal communities. These findings evaluated the risk range of coal mining on AMF and soil fungal communities and elucidated the microbial response strategy to mining disturbance.